Anandtech did put a special tape, Kapton tape that was 2mm thick that did help the witht he attenuation. It's in their last article testing 4.01 iOs.
http://www.anandtech.com/show/3821/iphone-4-redux-analyzing-apples-ios-41-signal-fix/1
Awesome link. Thanks for posting this. This is exactly the kind of read I was looking for.